Indicating device



July 10, 1951 R. A. PIRIE INDICATING DEVICE 3 Sheets-Sheet 1 Filed Sept. 23, 1948 bm, NN QN mmv (man Ayrnvf Pff/e 3f Nal-t Mure, Cul/ d' 509 July lo, 195,] R. A. PIRIE 2,560,304

INDICATING DEVICE 3 Sheets-Sheet 2 Filed Sept. 23, 1948 N VPN 701? Nm Adv/lug* Hg@ 9 mns 15m] Affaire/.s

July 10 1951 R. A. P|R|E 2,560,304

INDICATING DEVICE Filed Sept. 23, 1948 3 Sheets-Sheet 5 fig. 3.

Patented July 10, Q

INDICATING DEVICE Ronald. ,Anthony assigner to Saunder i Wight, England East Cowes, Isle of Pirie, Isle of Wight, England,

s-Roe Limited, Osborne,

Application September 23, 1948, Serial No. 50,825 In Great Britain September 25, 1947 8 Claims.

This invention relates to apparatus including a pair of motors arranged to drive a torque shaft through a dierential gear, and an operating member movable in opposite directions to cause the motor shafts to rotate forwardly or in reverse.

One specific application of the invention is to power operated ilying control systems of the kind described in United States application Serial No. 788,869, now Patent No. 2,517,680, comprising a pair of motors arranged to drive, through a diiferential gear, a torque shaft for operating the control surface, and a pilots control member effective, when moved, to cause the motors to rotate the shaft by an amount and in a direction determined by the amplitude and direction of the movement of the control member,

The purpose of duplicating the motors is to ensure that, in the event of failure of one of them, the other will be available to impart movement to the power shaft, when required. In the event, however, of total failure of one of the mo.- tors, the failed motor may in some circumstances be driven in reverse by the other motor through the differential gear, with the result that no movement will be imparted to the torque shaft.

With a View to meeting this contingency the invention provides a safety device which remains ineiiective so long as the motor shafts rotate in the same direction but is rendered operative, by rotation of the motor shafts in opposite directions, to give a warning signal, so that an attendant may stop the failed motor. Alternatively the safety device may be arranged itself to stop the failed motor.

In the flying control system described in United States application Serial No. 788,869, an irreversible drive is provided between each motor and the differential gear or alternatively hydraulic motors are used, each driven by a variable delivery hydraulic pump in turn driven by a constantly running electric motor, each hydraulic motor being tted with a mechanical lock which is normally held in the free position by the fluid pressure, but which is spring loaded so as to move, in the event of pressure failure, into position to lock the motor against reverse rotation. The Warning device according to the invention caters for the possibility of mechanical failure of the hydraulic motor which might occur while the iiuid pressure was effective to hold the Ylock inoperative. In this case, the warning device would Show the pilot immediately one .of the motors is running in reverse, whereupon he may, by switch- :ing olf the electric motor driving the pump as sociated with the failed hydraulic motor, cause the mechanical lock to operate, due to cutting off the hydraulic pressure, to lock thefailedhydraulic motor. Alternatively, the warning system, as indicated above, may be arranged to switch off the electric motor automatically. Moreover, the warning system renders unnecessary the provision of an irreversible drive between eachmotor and the differential gear.

In addition to providing a warning when the motor shafts are turning in opposite directions, due to failure of one of the motors, the warning system according to the invention may also, as described later, be arranged to give a warning when either of the motors is giving a reduced output in power and speed.

Some alternative forms of warning device for power-operated Iiying control Systems according to the invention willV now be described in detail, by way of example, with reference to the accom.- panying drawings in which:

Fig. 1 is a diagrammatic layout of a dying control system according to United States application Serial No. 788,869, and associated warning device,

Fig. 2 is an elevation, partly in section, showing the differential gear, the motor shafts and associated members for actuating the warning device in the case of failure of either motor, and

Figs. 3 and 4 are diagrams showing forms of warning device, alternative to that shown in Fig. 1, for showing the -pilot when the motors are giving different outputs.

Like reference characters designate like parts throughout the figures.

As explained in United States application Serial No. 788,869 a torque shaft I for imparting movement to the .dying control surface (e. Vg. an elevator) is driven, through a dierential gear Il, by a pair of hydraulic motors l2, l2a. Parts associated with the motor 12a bear the saine reference numerals as the Corresponding parts associated with the motor l2, with the Suix a- The motors l2, l2a are driven by variable delivery hydraulic pumps 53, 53a which, in turn, are driven by constantly running electric motors 1.4, i421 The pilots control column l5 is Qonnec-ted, by connecting rods i6, 16a, with the operating levers Il, lla of ,a pair of Selsyn transmitters 18, 18e. These levers, when moved, leffect corresponding movement of Selsyn receivers i9, I9@ which cause the hydraulic pumps i3, 13e to commence delivery. The hydraulic vmotors l2, l2a then rotate their shafts 20, 2da in thesame direction causing the planet .carrier 2l, and planet bodily about the axes of the motor shafts 25, 20a, thereby through gear wheels 22, 23, rotating the torque shaft I6. As described in United States application Serial No. 788,869 follow-up gears 25, 25a cause the pumps I3, I32i to cease delivery when the torque shaft il) has executed a movement determined in magnitude and direction by the magnitude and direction of the movement of the control column It will be convenient first to describe the warning device for intimating to the pilot that the motors I2, I2a are running at diirerent speeds. Each motor is arranged to drive a dynamo, dynamo 25 being driven from motor I2 by gear wheels 2, 2B, and dynamo 26aL being driven from motor i2EL by gear wheels 21a, 288L The dynamos 25, 26a are connected in a bridge circuit with a galvanometer 29 on the pilots control panel, the galvanometer 29 giving a Zero indication when the motors I2, I2a are running at equal speeds but showing a deflection to left or right from its zero indication according to which motor is failing to develop full power In an alternative arrangement shown in Fig. 3, the dynamos are replaced by governors 3U, 30a, driven by the motors through gears 2l, 25a and cooperating with pivoted contact arms 3I, Sla associated with variable resistances 32, 32a and each arranged to operate one of the arms, as the speed of the associated motor changes, to vary the associated resistance accordingly. The resistances 32, 32a are connected in a bridge circuit with a galvanometer 29 which shows a zero deflection when the motors are running at the same speed and the resistances are therefore equal. Unbalance as between the speeds of the motors will render the resistances 32, 32a unequal and result in an appropriate movement of the galvanometer needle to show which of the motors is failing to develop full power.

In a third arrangement, shown in Fig. 4, the speed indicators are again governors 30, 30a and cooperate with a yoke 33 mounted on a pivot pin 34 movable in a slot 35 in a supporting member 35, which slot extends parallel to the governor spindles. When the motors are running at equal speeds collars 31, 3Ia on the governors, which act in cooperation with the ends of the yoke 33, maintain the latter in a central position, equal change in speed of the motors merely causing the pin 34 to travel along the slot 35. When there is difference in speed between the motors, the governors will cause the yoke 33 to rock about its pivot pin 34, whereupon an extension 38 of the yoke rocks a pivoted stirrup 39` and causes one or other of a pair of switches 40, 40a to be closed, depending on the direction in which the yoke rocks from its central position. Closing of either of switches 40, 4Iia lights an associated lamp 4I or 4Ia on the pilots control panel. According as to which of the lamps 4I, lI is lit the pilot can tell which of the motors is running with decient power.

The Various forms of apparatus so ar described are effective to show the pilot when a motor is failing to develop full power and which of the motors is so defective. They cannot, however, give an indication of total failure of the motor since the motor will then run in reverse, and the apparatus in question, in all its forms, aords an indication of motor speed only and not also of the direction of rotation of the motor shaft.

The apparatus for showing when the motor wheels 24, to rotate fi shafts are rotating in opposite directions is shown diagrammatically in Fig. l, and in practical form in Fig. 2 and will be first explained with reference to Fig. l.

rihe motor shafts 2t, 263e carry gear wheels 42, 42a meshing respectively with gear wheels 43, 43eA each having a screw threaded connection with one of a pair of reciprocating members 44, 54a. The members 44, ida have squared ends passing through square holes in abutments 55, 45a and are thus held against rotation, and they are normally held in the neutral position shown by centering springs d5, 46a.

Normally the motor shafts 25, 20a will turn in the same direction, and when the motors are rendered operative, the reciprocating members f1.4, 44a will be caused, by the screw threads 4l, 47a to move in the same direction to close, according to their direction of movement, either switches 4S, 55a or switches 19, 49a. The screw threads 4l, Via are short so that after initial movement of the reciprocating members 44, 44u, the gear wheels 43, ita bec me disengaged therefrom and thereafter free wheel until the direction of rotation of the motors is reversed. When this takes place the springs 45, 45a cause re-engagement or the screw threads 4l', :l1a to cause rapid movement of the reciprocating members 44, 442L through the neutral position and beyond it in the other direction to a position in which the gear wheels 43, 33a can again free wheel.

Each of the connecting rods I5, I5a between the pilots control column I5 and the Selsyn transmitters li, il@ is broken, the two halves carrying switch contacts 55, 55a normally held apart by springs 5I, Sia interposed between the two halves of the rod. Whatever position the control column occupies, that switch 50 or 5i?a towards which it is moved will close, due to compression o its associated spring 5I, or 5W, and will remain closed until the movement of the control member has ceased, whereupon the spring will open further movement to that part of the connect-A ing rod which is attached to the transmitter.

The arrangement is such that movement to the right of the control column I5 will causethe motors to rotate in a direction such that the reciprocating members 44, 44L move to the right, while movement to the left of the control column will cause the reciprocating members 44, 44@L to move to the left.

rI he switches 5t, 5ta associated with the control column and those 48, 5321, 59, I9a associated with the reciprocating members 44, 44a are wired in circuit with a pair of warning lamps 52, 52a, one allotted to each motor, and a battery 53 in such a way that closure of the right hand control column switch 55@ prepares a circuit for lighting the lamps through the left hand reciprocating member switches d, 43a, while closure of the other control column switch 50 prepares a circuit for lighting the lamps 52, 522L through the right hand reciprocating member switches 49, 49a.

When the right hand control column switch 55a closes, the reciprocating members 44, 44a will, when both motors are operative, move to the right, closing their right hand switches 49, 49a. As at this time the left hand control column switch 55 is not closed, the lamps 52, 52a will not be lighted.

The lamps are connected in parallel, one 52 being connected across the battery 53 through the reciprocating member switches 48, 49 of the port motor I2 in parallel, and then through the the switch by imparting slight.

right hand control column switch 50a, and the other 52a being connected across the battery through the reciprocating member switches 48a, 49gb of the starboard motor l2a in parallel and then through the left hand control column switch 5I).

If, when the control column is moved to the right, the port motor i2 has failed, its reciprocating member 44 will, due to the port motor shaft '20 rotating in reverse, move to the left instead of the right, with the result that a circuit will be completed through switch 48 to light the warning lamp 52 allotted to indicate failure of the port motor. Similarly, if the starboard motor l2EL has failed, its reciprocating member 44a will move to the left and, by closing switch 48a, light the warning lamp 52a allotted to indicate failure of the starboard motor.

It will be understood that the lamps 52, 52e will be similarly lit to indicate which of the two motors has failed when the control column is moved to the left.

Instead of, or in addition to, arranging for lamps 52, `52a to be alternatively lit to indicate to the pilot which of the two motors has failed, the circuit may include solenoids 54, 54a arranged, when energised, to operate switches l55, 55a. v,Switch 55 is operated, just as lamp 52 is lit, when the port motor l2 has failed and when switch 55 is operated it switches oif the electric motor I4 driving the pump I3 associated with the port hydraulic motor i2. Similarly switch 55@- will be operated, in case of failure of the starboard motor |23, to switch off the electric motor l 4a driving the pump l 3a.

In the apparatus shown in Fig. 2, each motor shaft is divided into three parts, viz. a part v projecting from the motor casing, a part driving the differential gear and carrying the gear wheel 28, and an intermediate part 220, splined to the part |253 and coupled to the part 20 by a clutch 56. When either of the motors l2, |221 and associated parts of its power unit is removed for inspection or replacement, the associated sun wheel 571, or 57a, is locked against rotation by an extractor lock. Removal of the power unit is effected by removal of a screwed ring 5B or 583. When either power unit is removed, the splined section 220 of the motor shaft is urged outwardly by a spring 59, thereby bringing a pinion 60 carried by that section into engagement with a fixed pinion 6| and locking the sun wheel 51 againts rotation.

The gear wheels 28, 28a drive, through gear wheels 63, 63e, shafts 62, 62a carrying screw threads 41, 412- engaging the reciprocating members 44, 44a which are constituted by sleeves each having a pair of projections `|34, 65 engaging in slots in an outer casing 56, so that the reciprocating members are held against rotation. The projections 64, 642L coact with the centering springs `46, 46a, and the projections 65, 65a coact with microswitches 43, 49, 48a, 49a.

What I claim as my invention and desire to secure by Letters Patent is:

l. In a power operated flying control system for aircraft, the combination with a pilots operating member, a torque shaft for imparting movement to a control surface, a pair of power units each having an output shaft, a differential gear coupling said output shafts to said torque shaft, said power units being controlled by the pilots operating member and being operative, in response to movement of said operating member and by rotating their output shafts in the same direction, to move said torque shaft in a direction, and to an extent determined by the movement of said operating member, and a normally inoperative safety device, a pair of normally open switches which are arranged to close during movement of said operating member to prepare one of a, pair of electric circuits according to the direction of said movement, and to open -again on cessation of movement of said operating member, and means rendered operative on actuation of said output shafts in opposite directions to complete the prepared circuit and thereby to render said safety device operative.

2. A power operated flying control system for aircraft, comprising a pilots operating member, a torque shaft for imparting movement to a control surface, a pair of motors each having an output shaft, a differential gear coupling said output shafts to said torque shaft, said motors being operable by rotation of their output shafts in the same direction to move said torque shaft to a position determined by the movement imparted to said operating member, a pair of switch-operating members, one associated with each motor and each arranged, when the'associated motor is started, to move in one of two opposite directions from a neutral position according to the direction of rotation of the output shaft of the motor, a pair of switches associated with each switch-operating member which are arranged to be operated alternatively by said member, according to its direction of movement from the neutral position, a further pair o'f switches arranged to be operated alternatively by the pilots operating member when moved, according to its direction of movement, a source of current, an indicator adjacent the pilot and electrical connections between the switches, the source of current and the indicator such that the latter is non-responsive when the output shafts are rotating in the same direction but is rendered responsive, in the event of rotation in opposite directions oi the output shafts, to indicate to the pilot which output shaft is rotating in the direction reverse to that selected by the movement of the pilots operating member.

3. A power operated ying control system for aircraft as claimed in claim 2, in which each of said switch operating members is a reciprocating member, and comprising a rotary member driven by each output shaft and in screw threaded engagement with the associated reciprocating member, means for restraining each reciprocating member against rotation and springs for normally retaining said reciprocating members in neutral position, said recriprocating members being movable by the screw threads, when the motors are started, in a direction determined by the direction of rotation of the output shafts to operate the corresponding switches and the screw threads being short so that, after initial movement of the reciprocating members, the rotary members become disengaged therefrom.

4. A power operated flying control system for aircraft as claimed in claim 2, comprising a transmitter associated with each motor for operating said motor in a direction and to an extent determined by the movement imparted to the pilots operating member, and a split connecting rod joining the pilots operating member to each transmitter, each of said connecting rods being formed of two parts joined by a spring and one of said further switches being interposed between the two parts of each connecting rod, and the connecting rods being disposed so that the springs are selectively compressed to operate one or other of the associated switches in accordance with the .f

direction in which said operating member is moved.

5. In a power operated dying control system for aircraft, the combination with a pilots operating member, a torque shaft for imparting movement to a control surface, a pair of power units each having an output shaft, a differential gear coupling said output shafts to said torque shaft, said power units being controlled by the pilots operating member and being operative, in response to movement of said operating member and by rotating their output shafts in the same direction, to move said torque shaft in a direction and to an extent determined by the movement of said operating member, an indicator, a member associated with each output shaft and arranged to move, on rotation of said output shaft, in a direction determined by the direction of such rotation, said members being ineffective on said indicator so long as they move in the same direction. and means responsive conjointly to movement of said operating member and to movement of said members in opposite directions for operating said indicator to show which output shaft is moving in the direction reverse to that selected by said operating member. Y

6. In a power operated iiying control system for aircraft, the combination with a pilots operating member, a torque shaft for imparting movement to a control surface, a pair of power units each having an output shaft, a differential gear coupling said output shafts to said torque shaft, said power units being controlled by the pilots operating member and being operative, in response to movement of said operating member and by rotating their output shafts in the same direction, to move said torque shaft in a direction and to an extent determined by the movement of said operating member, a pair of normally open switches which are arranged to close during movement of said operating member to prepare one of a pair of circuits according to the direction of said movement and to open again on cessation of movement of said operating member, a member associated with each output shaft and arranged to move, on rotation of said output shaft, in a direction determined by the direction of such rotation, and means operative automatically in response to movement of said members in opposite directions to complete the prepared circuit and thereby to stop the power unit driving that output shaft which is moving in the direction-reverse to that selected by said operating member.

7. A power operated iiying control system for aircraft, comprising a pilots operating member, a torque shaft for importing movement to a control surface, a pair of motors controlled by said Operating member and each having an output shaft, a differential gear coupling said output shafts to said torque shaft, said motors being operable by rotation of their output shafts in the same direction to move said torque shaft in a direction and to a position determined by the movement imparted to said operating member, a pair of switch-operating members, one associated with each motor and each arranged, when the associated motor is started, to move in one of two opposite directions from a neutral position according to the direction of rotation of the output shaft of the motor, a pair of switches associated with each switch-operatingy member which are arranged to be operated alternatively by said member, according to its direction of movement from the neutral position, a further pair of switches arranged to be operated alternatively by the pilots operating member when moved, according to its direction of movement, a source of current, a normally inoperative safety device, and electrical connections between the switches, the source of current and the safety device for energizing said safety device in the event of rotation in opposite directions of the output shafts.

8. A power operated flying control system as claimed in claim 7, in which each motor is an electric motor and in which the safety device is constituted by a pair of solenoids which are selectively energized, in the event of rotation of said output shafts in opposite directions, to switch off the motor driving that output shaft which is moving in the direction reverse to that selected by the operating member.

RONALD ANTHONY PIRE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,091,242 Queen et al Mar. 24, 1911i 2,176,372 Allen Oct. 1'7, 1939 2,190,682 Satterlee Feb. 2i), 1940 2,205,330 Allen June 18, 194) 2,436,341 Weybrew Feb. 17, 1948 2,491,842 Weels Dec. 20, 1949 

